1. Field of the Invention
The present invention relates to a method of manufacturing a die having batch supply holes arranged at a batch supply side thereof, slits arranged at a batch discharge side of the die for forming the batch, and batch hold portions made of lateral holes, which are arranged at least at intersecting portions between the batch supply holes and the slits and are arranged corresponding to the slits, and particularly relates to a method of manufacturing a die for extruding honeycomb structural bodies having thin walls.
2. Description of the Related Art
As a die for extruding honeycomb structural bodies, there is a die comprising batch supply holes arranged at a batch supply side thereof, slits arranged at a batch discharge side of the die for forming the batch, and batch hold portions made of lateral holes, which are arranged at least at intersecting portions between the batch supply holes and the slits and are arranged corresponding to the slits. FIG. 1 is a schematic view showing one embodiment of a known die for forming honeycomb structural bodies disclosed in Japanese Patent Laid-Open Publication No. 53-137210 (JP-A-53-137210), and which is also an object of the present invention to be manufactured. In the embodiment shown in FIG. 1, a die 1 includes batch supply holes 2 arranged at a batch supply side of the die 1, slits 3 arranged at a batch discharge side of the die 1 for forming the batch. Batch hold portions of the die includelateral holes 4, which are arranged at least at intersecting portions between the batch supply holes 2 and the slits 3. The lateral holes 4 are arranged to correspond to the slits 3.
In the die 1 having the construction mentioned above, a dimension of the lateral hole 4 forming the batch hold portion is larger than that of the slit 3. Therefore, in order to manufacture the die 1 having the construction mentioned above, there is one technique, as disclosed in Japanese Patent Laid-Open Publication No. 56-40510 (JP-A-56-405 10), such that, a metal plate is connected by brazing to a metal block to which the batch supply holes 2 and the lateral holes 4 are preliminarily worked, and then a slit machining is performed with respect to the metal plate. Moreover, there is another technique, as disclosed in Japanese Patent Laid-Open Publication No. 56-119335 (JP-A-56-119335), such that, a metal plate is connected by brazing to a metal block to which the batch supply holes 2 and the lateral holes 4 are preliminary worked, and then a slit machining is performed with respect to the metal plate. A depression portion is formed in the metal plate and the depression portion of the metal plate is fitted by brazing to the metal block.
In the method of manufacturing the die 1 mentioned above, since the metal plate to which the slits are formed is connected by brazing to the metal block, a brazing portion becomes a weak point, and thus it is not possible to make stronger the slits to which a large load is applied during a batch extruding operation. Moreover, in an extreme case, the brazing portion is peeled off and the die does not function for extruding. Further, in the case that the depression portion of the metal plate is fitted to the metal block, it is difficult to fit all of the depression portions to a plurality of projections of the metal block at one operation, and thus a high precision die cannot be manufactured.
It is an object of the present invention to eliminate the drawbacks mentioned above and to provide a method of manufacturing a die, in which the manufactured die has a sufficient strength and a high precision.
According to the invention, a method of manufacturing a die having batch supply holes arranged at a batch supply side thereof, slits arranged at a batch discharge side thereof for forming the batch, and batch hold portions including lateral holes, which are arranged at least at intersecting portions between the batch supply holes and the slits and are arranged corresponding to the slits, include the following steps of:
(1) preparing a die main body;(2) performing a batch supply hole machining with respect to one principle plane of the die main body so as to form the batch supply holes; (3) performing a slit machining with respect to the other principle plane of the die main body so as to form the slits; and (4) performing a lateral hole machining so as to form the batch hold portions, which are arranged at least at intersecting portions in the die main body between the batch supply holes and the slits and are arranged corresponding to the slits to thereby form an integral die. The method may also include the following steps:
(1) preparing a main body; (2) performing a slit machining with respect to one principle plane of the die main body; (3) performing a lateral hole machining so as to form the batch hold portions arranged corresponding to the slits in the die main body; and (4) performing a batch supply hole machining with respect to the other principle plane of the die main body so as to form the batch supply holes to thereby form an integral die.
In the present invention, an order of the machining operations is different between the above described methods. However, in both cases, the batch supply hole machining, the slit machining and the lateral hole machining are performed with respect to the die main body in a predetermined order, and the die is manufactured integrally. Therefore, no brazing portion is existent in the die as compared with the known die, and thus it is possible to obtain the die having a sufficient strength and a high precision.
As a preferred embodiment of the present invention, the lateral hole machining is performed by at least one of wire electric-discharge machining, electrochemical machining, wire lap machining, diesinking electric-discharge machining, water-jet machining, drill machining and laser machining. In addition, the slit machining and the lateral hole machining are performed continuously by wire electric-discharge machining. Moreover, the manufactured die is used for extruding a thin wall honeycomb structural body having a rib thickness of not larger than 150 xcexcm. Further, a width of the slit is not larger than 250 xcexcm. Furthermore, the manufactured die is used for extruding a honeycomb structural body having a cell open rate of not smaller than 75%. Moreover, the manufactured die is used for extruding a honeycomb structural body having a cell density of not larger than 1800 cell/inch2. In all the preferred embodiments mentioned above, a die having improved properties can be manufactured easily.